We know that an underwater optical fibre cable includes a central filament which has helical grooves on its periphery in which the fibres are laid, while the gaps are sometimes filled with a viscous compound. This structure is usually protected by an insulating tape and/or an insulating sleeve, in PVC for instance. In order to absorb the tensile forces applied to the cable, a supporting armouring of steel wires wound helically in contiguous turns is built around the optical corre of the cable; this armouring is in turn protected externally by an extruded copper sleeve or by a longitudinally welded tape which forms a sleeve.
This assembly is also covered by a protective insulating sleeve.
In case accidental damage caused to the cable was to make the outer sleeve and the copper sleeve break in a particular point, it is very important that no high pressure sea water can get under the armouring of the cable and deteriorate this cable on great lengths.
The aim of this invention is to ensure longitudinal sealing of the cable at the armouring level.